As it is known, some species of fish, such as the Danio rerio, commonly known as zebrafish, are assuming an increasingly important role in scientific research laboratories. These fish have proved to be excellent indicators both for basic research studies and for pharmaceutical research studies, with application to developmental biology, embryology, toxicology, to the study of hereditary human diseases.
These fish, just as other fish or other animals in general, used for scientific experiments in various fields of biology which can range from biochemistry to behavioural biology, must naturally be raised and maintained in environmental conditions that are as stable and controlled as possible.
One of the various parameters that must be constantly monitored, is a natural diet, i.e., feeding.
In fact, it is known not only that food has a direct influence on the organism of the animal, but also that food is a highly polluting agent for the environment in which the animals live, particularly in the case of aquatic animals such as fish. When too much food is dispensed and is therefore not completely eaten by the fish, it rapidly pollutes the water, drastically deteriorating the quality, which naturally has a negative effect on the state of health of the fish.
Similarly, when excessive quantities of food are eaten by the fish, the water is polluted as a result of the excrement produced by the fish.
For these and other reasons well known in the sector and which shall not be listed in detail herein, controlling the food of animals, and in particular of fish, used in the laboratory for scientific experiments is an aspect of primary importance in order to guarantee appropriate scientific research.
It is also known that animal housing facilities destined to contain laboratory animals house a large quantity of animals. In the case of fish these animal housing facilities can occupy very large rooms in which there are thousands of tanks, each containing one or more fish, even ten or more fish for each tank. (Normally the maximum density commonly accepted is of 10 fish/l ).
It is therefore evident how dispensing of food to the animals housed in the animal housing facility is an activity that requires a great deal of time, which translates into high cost when this activity is performed manually by an operator or by a laboratory technician. Therefore, manual dispensing of the diet to the animals housed in the animal housing facility has numerous disadvantages.
As stated, the activity increases in terms of time and expense in proportion to the increase in the number of animals housed in the animal housing facility. Moreover, it is clear how dispensing of the diet by an operator introduces a margin of uncertainty regarding the quantity of food dispensed while, as stated, controlling the quantity of food dispensed to each animal is a fundamental aspect of the scientific experimentation activities to which said animals are subjected and for the quality of life thereof.
Furthermore, it is known that for fish used in aquaculture environments it is always advisable to dispense a given quantity of food in several rations during the day than a single dose of the same quantity. Therefore, the fish are normally fed from two to four times a day, with quantities of food that vary indicatively in a range limited to a few milligrams per fish, in the case of zebrafish.
Therefore, it is even more apparent that the drawbacks indicated above are even greater when considering that, in the case of fish used as experimental models, food is dispensed several times a day. Above all in the case of animal housing facilities comprising a large number of tanks, dispensing of food can therefore become an activity that occupies the researcher or laboratory technician for a considerably part of his time, and that this time is therefore taken away from the actual research activity.
Moreover, as stated, there may be several fish present in each tank. Therefore, another task entrusted to the operator is to establish each time the quantities of food to dispense to each tank according to the number of fish it contains. Also in this case, besides introducing the possibility of an error in defining the quantity of food, a considerable amount of time is required by an operator to determine and continuously check the quantities dispensed.
To provide an example, it has been found to be preferable to dispense food three times a day, once in the morning, once at midday and once in the afternoon, and obviously food must also be dispensed at the weekend. To date, where distribution of the diet is managed manually, there is a tendency to reduce dispensing during the weekend to only once a day to avoid burdening personnel with excessive work, which naturally translates into a cost for dedicated personnel. Moreover, it is apparent how dispensing food only once a day is not an optimum choice for the well-being of the animals, not only due to the fact that this introduces a variation in the diet which in any case reflects on the animals, but also because dispensing food only once a day usually implies that this ration is more abundant. Due to the morphology of the fish, which cannot eat food that deposits on the bottom, all food that is not assimilated immediately by the animals when it is a suspension in water, remains on the bottom of the tank causing the water to deteriorate in quality. Many species of fish, including zebrafish, due to their physical structure find it difficult to consume food once it has deposited at the bottom of the tank. In fact, these animals feed in the surface layers of the water column in which they live and have a “superior” mouth type. To provide another example of the extent of the problem, the time that the operator dedicates to the activity of dispensing food amounts to a cost of several thousands of euro per year for each structure or rack containing tens of tanks for housing fish.
A further problem linked in particular to the dispensing of food to aquatic organisms raised in specific tanks and which to date has prevented the production of automated systems for dispensing the diet, particularly solid diet, is linked to the environmental conditions found in the animal housing facility. In fact, it is known that the temperature and ambient humidity conditions in housing facilities for aquatic organisms have a negative influence on the feed. As the water inside the tanks is maintained at a temperature of around 27-28° C., the ambient temperature is normally around 25° C., with a humidity that can even reach values of 70%.
In these conditions, the feed forming the solid diet tends to become compacted, as it absorbs the humidity in the air, in practice making it necessary for the operator to distribute the feed by hand with particular measures.
A negative aspect worthy of notice is represented by the high probability of spilling the diet outside the specific holes. The result is that of obtaining large quantities of organic material which act as a substrate for the growth of undesirable organisms such as moulds, bacteria and insects. Often, this problem is sufficient for inspection bodies to refuse to issue the certificates required for the good management of an animal housing facility (e.g., IACUC in the USA).
Finally, but of no less importance, the discomforts to which researchers and laboratory technicians (animal technologists) are subjected while dispensing food to the tanks and therefore to the animals must also be mentioned, caused by the fact that structures have not been designed with attention to ergonomics. In fact, the structures supporting the tanks (racks) are often over 2 meters in height. Therefore, stools are often used in order to reach the tanks positioned on the top rows, resulting in a high risk of falls. The larger the dimension of the animal housing facility is, the greater the discomfort caused will be.